In-line friction twister and method of twisting

ABSTRACT

A method and apparatus is disclosed for imparting false twist to textile yarn wherein a friction twister is employed to impart a plurality of turns of twist to a strand of yarn for each revolution of the friction twister. The invention is particularly suited to situations wherein the yarn strand is moving rapidly. The disclosed frictional twister comprises two axially aligned hollow spindles containing frictional engagement means therein. The two spindles are driven by moving belts that contact the exterior circumferential surfaces of the spindles. Movable yarn guide means are provided to engage the yarn strand and assure adequate frictional engagement between the yarn strand and the frictional engagement means after the spindles are threaded up. Another embodiment of the friction twister has the capacity to handle a plurality of yarn strands simultaneously.

United States Patent Richter [54] IN-LINE FRICTION TWISTER AND METHOD OFTWISTING [52] 11.8. CI ..57/77.4, 57/l56 [51] Int. Cl. t ..D01h 7/92,D023 1/04 [58] Field of Search ..57/5 l-5l.6, 77.3-77.45,

[56] References Cited UNITED STATES PATENTS 3,066,473 12/1962 Maeda,.57/77.4 2,936,567 5/l960 Russell et al.... 2,936,570 5/l960 Arthur etal. ..57/77.4 X

[451 June 20, 1972 Primary Examiner-Donald E. Watkins AttorneyShafiertand Miller [57] ABSTRACT A method and apparatus is disclosed forimparting false twist to textile yarn wherein a friction twister isemployed to impart a plurality of turns of twist to a strand of yarn foreach revolution of the friction twister. The invention is particularlysuited to situations wherein the yarn strand is moving rapidly, Thedisclosed frictional twister comprises two axially aligned hollowspindles containing frictional engagement means therein. The twospindles are driven by moving belts that contact the exteriorcircumferential surfaces of the spindles. Movable yarn guide means areprovided to engage the yarn strand and assure adequate frictionalengagement between the yarn strand and the frictional engagement meansafter the spindles are threaded up. Another embodiment of the frictiontwister has the capacity to handle a plurality of yarn strandssimultaneously.

15 Claims, 5 Drawing figures PKTENTEDJmmm 3,670.488 sum ear 2 IN-LINEFRICTION TWISTER AND METHOD OF 'I'WIS'I'ING CROSS-REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of U.S. PatentApplication Ser. No. 25,559, filed Apr. 3, I970.

BACKGROUND OF THE PRESENT INVENTION The present invention relates to ayarn twister and the method of utilizing said twister. Moreparticularly, the invention relates to a yarn friction twister for falsetwisting one or more yarn strands and a method of using said frictiontwister.

One of the greatest drawbacks of a conventional false twisting bladewith a twist trapping pin such as that disclosed in U.S. Pat. No.3,044,247 to Hilbert is that one revolution of the spindle blade isnecessary to impart each revolution or turn of twist to the textilestrand of yarn. Since conventional false twist spindles are limited tocertain rotational speeds by the strength of conventional materials,there is a definite ceiling on the productivity realized by the use ofconventional false twist spindle blades.

In U.S. Pat. No. 2,936,567 to Russell, et al, U.S. Pat. No. 3,936,570 toArthur, et a1, and U.S. Pat. No. 3,029,591 to Scrafi', et al, there aredisclosed several types of devices or apparatus for false twisting atextile strand wherein one rotation of the false twister impartsnumerous rotations to the textile strand. However, the false twistapparatus disclosed in each of these three patents is subject to certaindisadvantages. For example, in none of these false twisting devices maymore than one yarn strand be processed at a time. Furthermore, none ofthese devices possess rotatable frictional elements that are readilyreplaceable. In addition, these prior devices do not contain a simpleand economical means for rotating the frictional surfaces that performthe actual twisting. Also, these prior devices may not be threaded-upquickly as would be necessary in certain applications wherein the yarnis moving at great speeds.

SUMMARY OF THE PRESENT INVENTION The friction twister of the presentinvention is particularly suited to applications wherein the process oftexturing thermoplastic yarns with a false-twist heat set into the yarnis combined with another process such as a spin-drawing of the yarn.

When first obtained from the manufacturer, thermoplastic yarn such asnylon or Dacron is of a given cross-sectional diameter and may require adrawing process to produce a yarn of proper size, strength and relatedproperties.

Generally, yarn is drawn over a series of rotating wheels or feed rollsas it is being heated, in order to draw the yarn into its desiredconfiguration. Because the length of the yarn is constantly increasing,it is necessary for progressive feed rolls to move at greater andgreater speeds in order to advance the yarn at a constant rate. Thelineal yarn speeds achieved in such processes are high in the order of4,000 5,000 yards per minute.

With such speeds, it becomes necessary to employ a falsetwist impartingmeans that is capable of quick thread-up, if the drawing process is tobe combined with a false-twist texturizing process. The false-twistimparting means of the present invention is capable of meeting thesecriteria.

The apparatus disclosed herein comprises two hollow spindlessubstantially coaxially aligned and mounted on a base plate for rotationabout their own axes. Because of the axial alignment of the two hollowspindles, a strand or end of yarn may be easily and quickly threadedthrough the hollow core of both spindles. Such threading may beaccomplished by the use of a simple wire hook or, in certain operations,may be accomplished by blowing or sucking the yarn through the spindleswith a jet of air or a vacuum.

It is to be emphasized that when the spindles are defined assubstantially coaxially aligned, what is meant is that the yamengagingfriction-twisting surfaces on the spindles are so positioned relative toeach other that they define a straight yarn path between them. Such astraight path allows the just described quick thread-up of a strand ofyarn that is moving rapidly. As is apparent, the size of the holethrough the spindles would allow slight deviations from absolute coaxialalignment but such deviations are intended to be within the scope of thepresent invention.

After the end of yarn is threaded through both spindles, a movable yarnguide with a major and minor axis of different lengths is moved throughthe space between the spindles and then, when offset from the axis ofthe spindles is pivoted on its mount so that the alignment of its majoraxis creates a yarn path there-about of a dimension greater than thedimension of the space between the spindles. In this manner the yarnassumes a generally "U" shaped configuration between the spindles but,because of the just described dimensional relationship, will contact agreater surface area of and be in good frictional engagement with theresilient friction twisting means located on the adjacent, facing endsof the two hollow spindles.

In other words, when the guide is offset from the axis of the twospindles, an operative yarn path is created that passes from onetwisting member to the guide and then to the second member. Yarn passingthrough such a path will contact a greater portion of the twistingmeans. When the twisting means is a torus-shaped element or member andwhen the yarn is passing through the hole through the toms, theincreased contact of the yarn path will be such to constitute an arc ofmore than of the surface of the torus and the frictional engagementbetween the twisting member and the yarn will be increased and improved.

As a second embodiment of the present invention, the yarn guide meansmay comprise one or a plurality of yarn guides each in a position fixedto but ofiset from the common axis of the two spindles. In such anembodiment, the end of yarn may be easily threaded through both spindlesand then, even if moving at a rapid speed, may be manually engaged witha threading tool and routed around the appropriate yarn guide. When aplurality of such yarn guides exist, a plurality of yarn ends may betwisted by this embodiment of the friction twister.

Accordingly, it is an object of the present invention to providefriction twister that is capable of being quickly and easily threaded upwith a rapidly moving strand of yarn, yet still assure an adequate twistimparting frictional engagement between the yarn and the frictionalengagement means of the friction twister.

It is another object of the frictional twister to provide a frictiontwister that is capable of simultaneously twisting a plurality oftextile strands.

It is another object of the present invention to provide a frictiontwister wherein the rotatable friction twisting surface is readilyreplaceable.

It is another object of the present invention to provide a frictiontwister wherein a textile strand at least approaches or departs thefrictional engagement means axially of the twister spindle.

It is yet another object of the present invention to provide a frictiontwister wherein two rotating spindles are combined with a plurality ofyarn guides in order to simultaneously false twist a plurality oftextile strands, yet, at the same time, maintain the plurality ofstrands physically separated to avoid entanglement thereof.

It is an additional object of the present invention to provide afriction twister that may be easily and quickly threaded.

It is still a further object of the present invention to provide afriction twister having a simple construction, relative ease ofmaintenance and economy of operation.

Other objects will appear hereinafter.

DESCRIPTION OF THE DRAWING FIG. 1 is a top view of an embodiment of thefriction twister of the present invention illustrating the axiallyaligned relationship of the spindles and showing the yarn guide means ina yarn engaging position in solid lines and a yarn non-engaging positionin dotted lines.

FIG. 2 is an end view of a portion of the friction twister taken on theplane line 22 of FIG. 1.

FIG. 3 is a side view of the friction twister of the present inventiontaken on the plane line 3-3 of FIG. 1.

FIG. 4 is a top view of another embodiment of the friction twister ofthe present invention with a plurality of fixed yarn guides tosimultaneously twist a plurality of yarn strands.

FIG. 5 is a sectional view of the friction twister of the presentinvention.

DESCRIPTION OF A PREFERRED EMBODIMENT A preferred embodiment of theapparatus of the instant invention may be more easily understood withparticular reference to the drawing. Two hollow spindles 20 and 20' arerotatably mounted on base plate by means of spindle brackets II and 11'.As is best visible in FIG. 3, spindle bracket 11 is mounted to baseplate It] by means of bracket screw 12.

When a plurality of like elements exist, primes will be used todesignate like elements. Hollow spindles and 20' are coaxially alignedwith each other and each has mounted on one end a resilient O-ring orfriction twisting means 21 and 21 respectively. These O-rings aretorus-shaped and may be considered peripheral twisting members as theyarn will contact the internal peripheral surface of the rings. The axisof the torus hole corresponds to the rotational axis of the spindle. Theends of spindles 20 and 20' that have friction twisting or engagingmeans 2! and 21' mounted thereon face each other and are spaced apart sothat a given distance exists between friction engaging means 2! andfriction engaging means 21'.

The hollow spindles are mounted in spindle brackets 11 and ll in amanner that will be described in greater detail below but which permitsrotation about the axis of the hollow spindles. Spindles 20 and 20 aredriven or rotated about their own axes by driving belts and 30',respectively. As is best visible in FIG. 2, driving belt 30 contacts theouter circumferential surface of spindle 20 and, as drive belt 30 movespast spindle 20, the frictional engagement therewith will rotate spindle20 about its own axis.

With particular reference to FIG. 2, yarn guide slide bar 40 is rigidlymounted to base late 10 by slide bar support members 4i and 42. Thesesupport members are mounted to base plate 10 by slide bar screws andnuts 43 and 44. Yarn guide slide bar 40 is mounted midway betweenspindle 20 and spindle 20' and is substantially perpendicular to theaxis of the spindles.

Double lobe yarn guide 50 is mounted on yarn guide slide bar 40 in amanner that permits a sliding action along the extent of yarn guideslide bar 40. Yarn guide 50 is shown in two positions in FIG. 1. Thefirst position, in phantom lines, is the position the yarn guide assumesprior to its engagement with yarn strand Y. The second position, shownin solid lines, illustrates the position of yarn guide 50 as it isengaging yarn Y. Attention is directed to the fact that yarn guide 50has a major axis passing through screws 53 and 54 and a minor axisdisplaced 90 therefrom. In the aforementioned first position, the majoraxis of yarn guide 50 is aligned with slide bar 40 so that the yarnguide may be moved between spindles 20 and 20'. In the second position,the major axis of guide 50 is offset from and parallel to the axis ofthe spindles for a purpose to be described below.

With particular reference to FIG. 3, double lobe yarn guide 50 ismounted by means of yarn guide screws 53 and S4 to yarn guide bracket52. Yarn guide bracket 52 has formed therethrough bracket pivot hole 57.A slide shoe 55 is formed in a manner to fit over and embrace yarn guideslide bar 40 and is complimentarily formed so that slide shoe 55 is freeto slide along the extent of yarn guide slide bar 40. Slide shoe pin 56is attached to or integrally formed with slide shoe 55 and passesthrough bracket pivot hole 57 in yarn guide bracket 52. A springfastener 58 is employed to attach yarn guide bracket 52 to slide shoepin 56 in a manner that permits rotation of yarn guide bracket 52 andits attached double lobe yarn guide 50 about pin 56 of slide shoe 55 yetwill maintain yarn guide 50 in a given position. This feature ofrotatability of double lobe yam guide 50 is necessary so that the yarnguide may be passed or slid between the two spindles 20 and 20 yet,afier the yarn is engaged around the yarn guide, the guide may berotated so that its major axis is parallel to the axis of the spindles.As the major axis of guide 50 is greater than the distance between thetwo spindles, the yarn path will be distorted or pass around thefriction means in a manner to increase the frictional engagement betweenthe yarn and the friction engagement means 21 and 21'.

More specifically, and with particular reference to FIG. 1, yarn Y isseen passing through the hollow core of spindle 20, then passes throughgroove 51 of double lobe yarn guide 50, and then passes through thehollow core of spindle 20'. In applications where yarn Y is moving atvery great speeds, as for example in a machine that would combine afalse twisting process with a drawing process, yarn Y would first bepassed through both spindles 20 and 20' by means that would facilitate aspeedy thread up. One example of such a means would be an air jet or anair suction that would blow or draw yarn Y through the hollow cores ofboth spindles. It is then necessary to pass the yarn over frictionengaging means 21 and 21' in a manner such that the rotation of spindles20 and 20' will impart a false twist to yarn Y passing therethrough.

Double lobe yarn guide 50 is shown in FIG. 1 in phantom lines in aposition such that its minor axis is aligned with yarn guide slide bar40. As yarn guide 50 is slid through the space between spindle 20 and20, yarn Y is engaged in yarn guide groove 51 and, as the motion of yarnguide 50 continues past spindles 20 and 20', yarn Y is drawn against andin contact with an arc of greater than of the surface of frictionengaging means 21 and 21'.

Yarn guide 50 is then rotated about pin 56 of slide shoe 55 such thatthe distance from point A on yarn guide 50 to point B on yarn guide 50is greater than the distance between fric tion engaging means 21 andfriction engaging means 21'. Because of this dimensional relationship,yarn Y will be drawn about friction engaging means 21 and 21' at anangle that is illustrated in FIG. I and designated a. This angle ismeasured between the line of the yarn path and a plane passingperpendicular to the axis of the spindle.

The actual angle necessary to insure adequate frictional engagement is afunction of, among other parameters, the tension of the yarn, butgenerally is of the order of 5 to 15. While angle a is illustratedrelative to friction engaging means 21, it is understood that a similarangle exists between the yarn and a plane passing through frictionengaging means 21' and perpendicular to the axis of spindle 20'. As thetension of the yarn will vary throughout the friction twister, these twoangles are not necessarily the same, though they will be within severaldegrees of each other. The size of each lobe of yarn guide 50 willdetermine the corresponding yarn angle.

Spindles 20 and 20' are mounted for rotation in spindle brackets ll andII, respectively. With particular reference to FIG. 5, spindle 20 isshown attached to bracket 11' by means ofa cylindrical spindle mountingmember 23. Member 23 may be press fit into a hole in bracket ll or maybe rigidly mounted in some other conventional manner. Bearings 25 may beneedle, ball or other suitable bearings and are positioned betweenmounting member 23 and hollow spindle core 24. Bearings 25 are separatedby hearing spacer 26. Hollow spindle core 24 is attached to orintegrally formed with cylindrical spindle body 22.

Belt 30' contacts the outer surface of spindle body 22 and when belt 30'is moved past the spindle, spindle body 22 and hollow spindle core 24will rotate about the axis of the spindle.

Spindle body 22 has formed in one end a friction member recess 27 thatis shaped complimentarily to O-ring or friction twisting means 21'. Itis to be noted that the O-ring is firmly seated within recess 27 so thatits midline is recessed below the end wall of spindle body 22. By suchseating the O-rings are prevented from being pulled out of the spindleduring rota tion thereof. The natural resilience of the O-ring issufficient to hold it within recess 27 yet removal for purposes ofreplacement is easily accomplished. It is noted that as one side of theO-ring is worn from contact with the yarn, the O-ring need only bereversed to present a new face to the yarn.

Another embodiment of the present invention permits the simultaneoustwisting of a plurality of yarn strands. With particular reference toFIG. 4, stationary yarn guides 60 and 60' are shown attached to baseplate by means of yarn guide mounts 62 and 62'. Both yarn guides areoffset from the axis of the two spindles 20 and 20' so that a strand ofyarn may be easily and quickly drawn through the hollows of bothspindles. A yarn threading tool or hook may then be employed to engage astrand of yarn and route it around the appropriate yarn guide, evenwhile the strand of yarn is rapidly moving.

Each yarn guide has a yarn guide groove 61 formed therein and thedimension of the diameter of the yarn guide, as measured from the bottomof the groove to bottom of the groove, is to exceed the dimension of thedistance between the two 0- rings on spindles 20 and 20'. Thisdimensional relationship permits the yarn strand to contact a greaterportion of the O- ring surface to thereby increase the frictionalengagement therebetween. As mentioned with respect to the embodimentillustrated in FIG. 1, the angle thus formed between the path of theyarn strand and a plane passing through the O-ring and perpendicular tothe axis of the spindle may be in the order of 5 to l5, although thesevalues are not critical. The objective is merely to insure that adequatefrictional engagement of the strand with the O-ring is maintainedthroughout the twisting cycle.

While the embodiment of FIG. 4 is shown with two yarn guides 60 and 60',it is to be understood that a greater number of yarn guides may bepositioned in a circle a full 360 about the axis of the two spindles.The practical limitation on the number of yarn guides possible, andhence the number of yarn strands that may be simultaneously processed,is only that sufficient space must be allowed between the strands asthey pass through the spindle to avoid entanglement during operation.

Several further factors are to be noted. The internal diameter of O-ring21 or 21' maybe less than the internal diameter of hollow spindle core24 so that yarn passing over the O-ring will be held clear of theinternal surface of core 24. In this manner, undesirable contact betweenthe yarn and the core will be avoided.

Additionally, although a strand of yarn passes through two separatespindles in each embodiment of the present invention, the twistingaction of the O-ring of each spindle is not additive. One O-ring impartsa given number of turns of twist to the strand but then the secondO-ring does not add more turns of twist to the strand. Instead, eachmember cooperates with the other in the impartation of a given number ofturns of twist to the yarn strand.

Of further interest is the fact that the increased length of the yarnpath as it passes around the yarn guide permits an increased period oftime in which the yarn may cool and set the twist that has been impartedthereto. It is a well know phenomenon that a false twisting deviceimparts a false twist upstream in a yarn moving therethrough but removesthe false twist downstream of the device. With particular reference toFIG. 1, yarn Y is passing from spindle 20 to spindle 20. Twist will beimparted to the yarn upstream of spindle 20 and will be removeddownstream of spindle 20'. The yarn will still be twisted as it passesabout the yarn 50 and, as no heat is being added to the yarn in thiszone, the yarn will have a path of increased length in which to cool.This feature is particularly advantageous when the lineal speed of theyarn is very high. Such speeds would be encountered in, for example, aprocess combining a drawing operation with a false twist texturizingoperation.

The number of twists that may be imparted to an end of yarn with thefriction twister of the instant invention may be appreciated by thefollowing example. A friction member with 0.328 inch inside diameter andan 0.702 inch outside diameter (and a circular cross section with adiameter of 0.187 inch) will create a twisting diameter of aboutone-half an inch. If the spindle friction member has a twisting diameterof one-half an inch and a 15 denier filament with a diameter ofapproximately 0.00l inch is used, a ratio of 1:500 will exist betweenthe two. With such a ratio, every rotation of the friction spindlemember will produce 500 revolutions of the yarn end. Consequently, ifthe spindle is rotating at 20,000 rovolutions per minute, the end of theyarn would have 10,000,000 revolutions per minute imparted thereto. Thenumber 0s twists imparted per unit length is, of course, a function ofthe speed at which the yarn is traveling through the twister. Thus, itcan be seen that the friction twister of the instant invention iscapable of imparting a very large number of twists to an end of yarnrunning through the device.

OPERATION In operation, yarn guide 50 is positioned as shown in solidlines in FIG. 1. Friction engaging means 21 and 21' and yarn guide 50define an operative yarn path for yarn Y.

The strand of yarn is led toward O-ring 21 and is frictionally engagedby the interior surface of the O-ring. The strand contacts somewhat overof the surface of the Oring (as seen in cross section), the degrees over90 being a function of the size of angle a. It is only necessary thatthe contact between the yarn and the O-ring be sufficient to assure agood twist-imparting action.

The yarn strand Y then departs O-ring 21 as the yarn path passes towardpoint A of yarn guide 50. After passing around the yarn guide the yarnpath passes from point B of yarn guide 50 toward O-ring 21. As isapparent from an inspection of FIG. I, the yarn path from point B toO-ring 21' is substantially the reverse of the yarn path from O-ring 21to point A, although angle a and its corresponding angle with O-ring 21'prevents this reversal from being a precise reversal.

Yarn Y then contacts O-ring 21 and is frictionally engaged thereby.After passing over a sufficient surface area to assure a good twistimparting action, the yarn strand Y continues in the yarn path on to thenext step in the textile process, such as cooling and take-up.

Throughout the entire false-twisting of the yarn, the tension in theyarn must be controlled and maintained in a manner that will assure agood twist imparting action yet avoid yarn jump and chatter. Too great atension will cause the yarn to jump on the surface of the O-ring,causing uneven wear of the O-ring and afi'ecting the twist impartingaction. Tension may be controlled in a number of well known methods suchas positively driven feed rolls before and after the false-twist spindleassembly.

The direction of twist imparted by the in-line friction twister of thepresent invention may be governed in one of several ways. A simplereversal of the direction of travel of both belts 30 and 30' will rotateboth spindles 20 and 20 in a different direction, thereby changing thedirection of the twist. In the alternative, if the driving belts moveonly in one direction, contact with the bottom surface of the spindleswill drive them in one direction and contact with the top surface willdrive them in the other direction. It is of course understood that otherdriving apparatus may be used in place of the belts 30 and 30.

The thread-up of the device is such that the false twister of thepresent invention may be used with yarn that is moving rapidly. The yarnmay be passed from one twisting surface of a twisting member to theother so that the path of the yarn defines a straight line. If eachtwist member is located in a twisting zone, the straight line passesfrom one zone to the other.

The yarn may be stationary or may be moving through the two zones but asegment of the yarn is now displaced from its straight yarn path byeither moving the guide past the spindles or, if the guide isstationary, engaging the yarn with a threading tool and positioning itabout the guide. Thread-up is now complete.

It should be apparent that the present invention may be embodied inother specific forms without departing from the spirit or essentialattributes thereof, all of which are intended to be encompassed by theappended claims.

lCLAlM:

1. Apparatus for imparting false twist to thermoplastic yarn comprisingtwo separate yarn-engaging friction-twisting means each aflixed to arotatably mounted spindle, said spindles being in substantial coaxialalignment and spaced apart by a given distance, and yarn guide meanscooperating with said twisting means to define an operative yarn pathpassing from one of said twisting means to said guide means and then tothe other of said twisting means.

2. Apparatus according to claim 1 wherein each of said yarn-engagingfriction-twisting means comprises a torusshaped resilient member mountedfor rotation about the axis of the hole of said torus.

3. Apparatus according to claim 2 wherein said guide means is offsetfrom said torus-shaped resilient members so that the yarn passingthrough said operative yarn path contacts a portion of said torus-shapedmember constituting an arc of more than 90 whereby adequate frictionalengagement is assured between said toms-shaped resilient members andyarn passing through said operative yarn path.

4. Apparatus according to claim 3 wherein said yarn guide means is oneof a plurality of yarn guide means, each establishing a separateoperative yarn path with said torus-shaped resilient members whereby aplurality of yarn strands may be simultaneously false twisted.

5. Apparatus according to claim 2 wherein said guide means is slideablymounted on bracket means for displacement between a thread-up positionand an operative position whereby yarn initially passing direct from oneof said torusshaped members to the other of said torus-shaped membersmay be carried to said operative position by the displacement of saidguide means.

6. Apparatus for imparting false twist to thermoplastic yarn comprisinga base plate, two hollow spindles rotatably mounted on said base platein substantial coaxial alignment and spaced apart by a given distance, atorusshaped friction' twisting member mounted on each of said spindles,guide means cooperating with said twisting members to define anoperative yarn path passing from one of said members to said guide meansand then to the other of said members and drive means to rotate eachspindle and its associated torus-shaped member to thereby impart falsetwist to a strand of yarn passing through said path.

7. Apparatus according to claim 6 wherein said torusshaped members aremounted on the adjacent facing ends of said spindles.

8. Apparatus according to claim 6 wherein said drive means comprise twodriving belts, one for each spindle and contacting the outercircumferential surface of said spindle.

9. Apparatus according to claim 6 wherein said base plate has mountedthereon a slide bar and said guide means is slideable along said slidebar.

10. Apparatus according to claim 9 wherein said slide bar extendssubstantially perpendicular to the axis of said hollow spindles and saidguide means has a major axis and a minor axis and is pivotally mountedto a guide bracket, said guide bracket being slideably mounted to saidslide bar.

ll. Apparatus according to claim "I wherein said guide means ispositioned with said major axis parallel to but offset from the axis ofsaid hollow spindles when yarn is passing through said operative yarnpath.

12. Apparatus according to claim 6 wherein said guide means is one of aplurality of am guide means, each rigidly attached to said base plate anesta lishing a separate operative yarn path with said torus-shapedmembers whereby a plurality of yarn strands may be simultaneously falsetwisted.

13. In the process for threading-up a false twisting apparatus, theimprovement comprising the steps of passing a strand of yarn in a firststraight path through a first false twisting zone and a second straightpath through a second false twisting zone in a manner that both of saidpaths are coaxially aligned with each other and said yarn strand definesa straight line between said zones, and subsequently positioning asegment of said strand of yarn around a guide means so that said segmentdeviates from said straight line.

14. The improved process of Claim 13 wherein said strand of yarn ismoving between said zones simultaneously with said step of positioningsaid segment around said guide means.

15. in a process of threadingmp a false twisting apparatus, theimprovement comprising the steps of advancing a strand of yarn in astraight path toward said false twisting apparatus, continuing toadvance said yarn in said path while passing said strand across thetwisting surface of two friction twisting members in said false twistingapparatus, and subsequently engaging said yarn between said surfaces anddisplacing said yarn about a guide to increase the contact andfrictional engagement between said yarn and both of said twistingsurfaces.

1. Apparatus for imparting false twist to thermoplastic yarn comprisingtwo separate yarn-engaging friction-twisting means each affixed to arotatably mounted spindle, said spindles being in substantial coaxialalignment and spaced apart by a given distance, and yarn guide meanscooperating with said twisting means to define an operative yarn pathpassing from one of said twisting means to said guide means and then tothe other of said twisting means.
 2. Apparatus according to claim 1wherein each of said yarn-engaging friction-twisting means comprises atorus-shaped resilient member mounted for rotation about the axis of thehole of said torus.
 3. APparatus according to claim 2 wherein said guidemeans is offset from said torus-shaped resilient members so that theyarn passing through said operative yarn path contacts a portion of saidtorus-shaped member constituting an arc of more than 90* wherebyadequate frictional engagement is assured between said torus-shapedresilient members and yarn passing through said operative yarn path. 4.Apparatus according to claim 3 wherein said yarn guide means is one of aplurality of yarn guide means, each establishing a separate operativeyarn path with said torus-shaped resilient members whereby a pluralityof yarn strands may be simultaneously false twisted.
 5. Apparatusaccording to claim 2 wherein said guide means is slideably mounted onbracket means for displacement between a thread-up position and anoperative position whereby yarn initially passing direct from one ofsaid torus-shaped members to the other of said torus-shaped members maybe carried to said operative position by the displacement of said guidemeans.
 6. Apparatus for imparting false twist to thermoplastic yarncomprising a base plate, two hollow spindles rotatably mounted on saidbase plate in substantial coaxial alignment and spaced apart by a givendistance, a torus-shaped friction-twisting member mounted on each ofsaid spindles, guide means cooperating with said twisting members todefine an operative yarn path passing from one of said members to saidguide means and then to the other of said members and drive means torotate each spindle and its associated torus-shaped member to therebyimpart false twist to a strand of yarn passing through said path. 7.Apparatus according to claim 6 wherein said torus-shaped members aremounted on the adjacent facing ends of said spindles.
 8. Apparatusaccording to claim 6 wherein said drive means comprise two drivingbelts, one for each spindle and contacting the outer circumferentialsurface of said spindle.
 9. Apparatus according to claim 6 wherein saidbase plate has mounted thereon a slide bar and said guide means isslideable along said slide bar.
 10. Apparatus according to claim 9wherein said slide bar extends substantially perpendicular to the axisof said hollow spindles and said guide means has a major axis and aminor axis and is pivotally mounted to a guide bracket, said guidebracket being slideably mounted to said slide bar.
 11. Apparatusaccording to claim 10 wherein said guide means is positioned with saidmajor axis parallel to but offset from the axis of said hollow spindleswhen yarn is passing through said operative yarn path.
 12. Apparatusaccording to claim 6 wherein said guide means is one of a plurality ofyarn guide means, each rigidly attached to said base plate andestablishing a separate operative yarn path with said torus-shapedmembers whereby a plurality of yarn strands may be simultaneously falsetwisted.
 13. In the process for threading-up a false twisting apparatus,the improvement comprising the steps of passing a strand of yarn in afirst straight path through a first false twisting zone and a secondstraight path through a second false twisting zone in a manner that bothof said paths are coaxially aligned with each other and said yarn stranddefines a straight line between said zones, and subsequently positioninga segment of said strand of yarn around a guide means so that saidsegment deviates from said straight line.
 14. The improved process ofclaim 13 wherein said strand of yarn is moving between said zonessimultaneously with said step of positioning said segment around saidguide means.
 15. In a process of threading-up a false twistingapparatus, the improvement comprising the steps of advancing a strand ofyarn in a straight path toward said false twisting apparatus, continuingto advance said yarn in said path while passing said strand across thetwisting surface of two friction twisting members in said false twistingapparatus, and subsequently engaging said yarn between saId surfaces anddisplacing said yarn about a guide to increase the contact andfrictional engagement between said yarn and both of said twistingsurfaces.